Mac OS X 10.7, better known as Lion, is an impressive update to the Mac operating system. In addition to its many important features, Apple finally removed one of my longest-running pet peeves and now allows you to drag windows from any side. Yay!

On the other hand, scrolling is backward (unless you tweak a setting), so you win some, and you lose some.

Where Lion can't be used

I'm doing a specialized video project that requires a certain piece of software that only runs on the Mac. Knowing (or at least suspecting) that Apple was about to refresh the Mac mini, I held off on buying one until the new Lion machines were announced last week. At that point, I pulled the trigger on a Lion-based Mac mini server, and it arrived the next day.

I immediately installed the Canon EOS Utility and discovered...oops! Canon doesn't support Lion for its DSLR cameras. A quick look at the Canon page shows support only for up to the previous version, Mac OS X 10.6, better known as Snow Leopard.

It's also not clear how long it will be before Canon provides Lion support for cameras. A quick look at the company's dedicated Lion-support page lists only printers, multifunction printers, and scanners. There's no mention of cameras.

Being the intrepid geek that I am, I decided to ignore the version compatibility statements and just try running the EOS Utility software. Sadly, I was thwarted.

The problem isn't limited to Canon. On July 22, Nikon announced "plans to test" their software for compatibility with Lion, but details about when the software will be compatible were limited to the vague statement, "We will announce our plans regarding full compatibility once testing is complete."

It quickly became clear to me that, as much as I yearned for windows that can be resized from all sides, Lion wasn't going to cut it for my particular DSLR processing needs. I would need to back-rev the machine to Snow Leopard.

This, by the way, isn't entirely Apple's fault. I know I've blamed Apple for a lot over the years, but most developers have had access to Lion developer versions for months, and nearly everyone knew that Rosetta (the PowerPC emulation environment) was going away with Lion.

Unfortunately, in moving on, there were programs left behind. Canon's EOS Utilities was the one I need to run. And, since I needed to run the EOS Utilities more than I needed Lion's new features, I decided to go back to Snow Leopard.

Later in this article, I'll show you how I eventually got Snow Leopard to run. Once it was installed, I had the bright idea of moving Snow Leopard's Rosetta installer from Snow Leopard to a running Lion install, and trying to run it. No dice. Even if you move the Rosetta installer to Lion, it won't actually work. Heh, nice try, eh?

In any case, let's get back to the how-to portion of our story.

Finding Snow Leopard

As it turns out, getting a copy of Snow Leopard was nearly impossible. Apple apparently doesn't offer a downloadable version of Snow Leopard, and so if you want a copy, you're likely to have to wait 2-4 weeks.

This is particularly ironic for a few reasons. First, Apple is requiring all pre-Snow Leopard Mac owners to first upgrade to Snow Leopard before they can access the Mac App Store and download Lion. No Snow Leopard, no upgrade to Lion. Second, Apple has been trying desperately to get out of the removable media business, and yet they're probably waiting on additional physical production runs to fulfill the demand for Snow Leopard.

In any case, after looking on Apple's site and looking on Amazon, calling my not-really-local Apple Store (it's an hour and a half away if traffic's on your side), and checking with all the Best Buys within an hour drive, I struck out.

I finally found a copy of Snow Leopard at a local Apple-specialist store, Visual Dynamics. This retailer pre-dates the Apple-owned stores and has still managed to hang on in the face of Apple's retail competition. This was a very nice store, but you can see how Apple supports its non-Apple branded retailers -- I had received my new Lion-based Mac mini before the store got their first new Lion-based machine from last week's new model introductions.

Installing Snow Leopard on the Lion-based Mac mini server proved to be more trouble than I expected. First, of course, the Mac mini server doesn't have a media slot. Fortunately, I have a spare USB-based external DVD drive, so I plugged that into the Mac mini, loaded the disk, and booted.

I held down the Option key (which is Mac-speak for "let me choose which disk to boot from"). I booted from the external DVD drive, saw the Apple logo load off the Snow Leopard DVD, and ... waited.

And waited.

And waited.

And waited.

I finally decided to reboot the system, and try again. I got the same result. Snow Leopard's installer hangs when trying to load on a new Lion-based machine.

Houston, we have a problem.

Apparently, Snow Leopard gets very confused when it sees the Lion restore partition on the new Mac's hard drives. I'm guessing this will also be a problem for those who upgrade to Lion, since the recovery partition is created automatically. As far as I could tell, this makes it impossible for the Snow Leopard DVD to boot on a Lion-prepared machine and install.

I needed to find a work-around. And I did.

Fortunately, I have certain super-powers. I can type a sequence of characters into a text field on a Web site called "The Google" and, upon my command, magical elves will scour the entire world, seeking what I need to know.

As is often the case, the deep truths we seek can be found in discussion boards.

And so it was. And so it came to pass that, with the help of the divine posters of the online board brotherhood, the Lion laid itself down upon the firmament and let the Snow Leopard boot unto the sacred Macintosh.

First, as it turns out, you're going to need two Macs to pull this off. I'm not sure you can back-rev your new Lion machine if you don't already have another Mac lying around. I could say something here about Apple products being easy to use, but the last time I said something negative about Apple, a bunch of acolytes tried to get me fired. Thanks for that, by the way.

So, I'm holding off the snark, for now at least.

Make sure you have your new Lion-based Mac and your old Mac on your desk. Be sure to find a Firewire 800 cable (at least my new Mac mini server doesn't support the old Firewire 400 cables). Shut both machines down.

Plug the Firewire cable into the new, Lion-based Mac and turn it on while at the same time holding the T key. This places the machine into "target" mode, which essentially turns the computer into an external hard drive. This, by the way, is a very cool Mac feature that -- at least to the best of my knowledge -- Windows doesn't have.

If you hold down the T key, the new Mac will boot up and display the Firewire logo on its screen. It will not boot into a GUI.

By the way, did you ever notice how similar the Firewire logo is to the radiation warning triform? Neither did I, until I started this little project:

Weird, huh?

Anyway, now that your new Mac is booted up and in target mode, boot up your old Mac. I left the Firewire cable out of the old Mac, and just booted it up. Once the old Mac was booted, then I plugged in the Firewire cable, and the old Mac suddenly had the new Mac's drives on its desktop, just like any other external drives.

The astute reader might have noticed I used the word drives (plural). One of the reasons I bought the Mac mini server was because it comes with two 7200RPM drives. I'm doing video and the two faster drives will be a big help.

The two-drive configuration makes this a much easier install. I merely installed Snow Leopard on one drive and left Lion on the other. If you only have one Lion drive, you may be able to partition it, and install Snow Leopard on the other partition, but that's a theory, only. I haven't tested it.

To make things easier, once I'd booted up on the old Mac and saw the hard drives from the new Mac on the desktop, I renamed the drives. The Lion boot drive was renamed to "Lion Server". The drive that would hold the back-rev Snow Leopard was renamed, creatively, "Snow Leopard".

Finally, make sure your old Mac has a DVD drive. If it doesn't, go find an external USB drive and use that. I'm guessing you could run the Leopard installer from an image or a USB key, but that's also something I didn't try.

Now you're ready to run the installer. Find your oh-so-precious Snow Leopard DVD and insert it into your old Mac's DVD drive.

The Snow Leopard installer will ask you where you want to install Snow Leopard. Here's where you want to be careful, and select your previously renamed "Snow Leopard" destination drive (remember, this is really the drive on the new Lion machine). Click next and let the install proceed. It took about forty minutes on my 2008-vintage iMac.

Once that's done, run the Combo update. It'll look like the Combo update is starting to update your old Mac, but that's just a fancy splash screen. Wait until the splash graphics run out of steam, and once again select your "Snow Leopard" drive living on your new Lion machine as the destination. This took about 20 minutes.

Once this process is all done, shut down your old Mac and unplug the Firewire cable. You'll have to hold down the power button on your new Mac and let it shut down as well.

Choosing your boot drive

Press the power button on your new Lion-based Mac and hold down the Option key. In a moment, you should see both the "Lion Server" and "Snow Leopard" drives (or your locally-named equivalents). Click the arrow under the Snow Leopard drive and wait for the system to boot.

If you followed all the steps I've outlined, you should find yourself booted into Snow Leopard. If you want to boot into Snow Leopard by default, go to System Preferences and select Startup Disk, and choose your Snow Leopard drive as the start drive.

Some final warnings

I am extremely nervous about an OS that doesn't come with disks. It feels unnatural. It also feels fast and loose with the system's security. What if, for example, you completely nuke your drives and the recovery partition? How do you recover?

Honestly, I'm guessing Apple's has a method beyond sending the machine back to the company for a warranty repair, but I haven't had a chance to research it. [Update: it does.] I did register my machine on the Mac App store, but the company still shows that if I want to download Lion Server, they'll charge me $49.99, so I don't know that I could reinstall without rebuying it.

The bottom line is this: these instructions have you screwing around with your OS on your brand-new machine. If you follow these instructions and something breaks, don't come crying to me. I can't guarantee this will all work and I've tried it on exactly one machine.

Your attempt could always go horribly wrong. If it does, you were warned. I, ZDNet, the CNET Professional Network, CBS Interactive, and all the company's associated properties disclaim any responsibility. You're on your own here.

Be careful. If you're not comfortable futzing around with OS installs that could go very, very bad, get some help.

Good luck, and may all your leopards be snowy ones.

So, what software have you found that works reliably on Lion and what doesn't? Are you, like me, holding back and running Snow Leopard because something's not compatible? What? Tell us in the TalkBacks below.